Nepenthes, also known as tropical pitcher plants, belong to the monotypic family, Nepenthaceae. They are carnivorous plants that produce specialized, cup-shaped, fluid-filled leaves (pitchers) that attract, capture, kill and digest insects and other small animals (McPherson & Robinson, 2012). Pitcher plants are known locally as periuk kera among the Malays of Peninsular Malaysia, kekuanga to the Dusun of Sabah, entuyud to the Iban and akah tuyud to the Melanau, Matu and Daro of Sarawak. In Brunei, the local Malays call it somboi-somboi (Adam & Hafiza, 2007).
Nepenthes gracilis was formally described by Pieter Willem Korthals in his 1839 monograph ‘Over het geslacht Nepenthes’ (Korthals, 1839). The epithet ‘gracilis’ is derived from Latin, meaning thin and slender, referring to the shape of the leaves and pitchers of this species. This species occurs in Thailand, Sumatra, Peninsular Malaysia, Singapore, Borneo and Sulawesi. In Peninsular Malaysia, it is the most widespread and common species from the lowlands to 800 m altitude, growing in open places, on poor, acidic waterlogged soil, ranging from the coasts, riversides, forest margins to freshwater swamps. It is also frequently found in disturbed areas, e.g., roadsides or old tin-mining land (Cheek & Jebb, 2012).
Nepenthes gracilis is a climber which can grow up to 10 m high, but it is more often a scrambler over small trees and shrubs. It may also grow as large clumps which produce abundant clusters of ground pitchers on young rosette plants and on side shoots at the base of the climbing stems, or along stems lying over the ground. The lower pitchers are small, cylindrical with a bulbous base, and can reach up to 11 cm tall with wings that are up to 5 mm wide. The upper pitchers are similar to the lower pitchers, but can reach up to 15 cm in height and have a narrow peristome with wings reduced to narrow ridges. In pitcher plants, the peristome is a reflexed ring (or partial ring) of tissue that surrounds the entrance to the digestive tube of these plants. It often possesses sharp, overhanging tooth-like projections which aid in prey retention and it is often studded with nectar secreting glands. The pitchers come in a variety of colours, from green throughout to dark purple on the outside with red speckles on the inner surfaces. An important distinguishing characteristic of N. gracilis is the structure of the leaf base which has no distinct petiole and decurrent margins (i.e., the leaf margins extend along the internode for some distance (Clarke, 2002). An inflorescence is produced from the tip of an upper branch of the slender pitcher. This inflorescence is erect and consists of flowers borne along the vertical stem. The flowers have been variously described as white, green, light red or brown. In Sumatra, this species is reported to be pollinated by moths (Clarke, 2001). After pollination, the flowers develop into specialized fruits known as capsules, which break open when ripe to release the seeds, which are then wind dispersed.
A decoction of the roots of N. gracilis has been reported as a treatment for stomach-ache and dysentery (Cheek & Jebb, 2001; Faridah-Hanum & Shamsul 2004).
Over-collection and illegal harvesting for the horticulture trade are major threats to many species of tropical pitcher plants. In addition, extensive habitat loss caused by agriculture, urban expansion and transport-related construction continue to destroy habitats throughout the range of this genus. Ex-situ conservation and propagation programmes are vital to ensure the survival of many species of Nepenthes. Such programmes can also potentially serve as repositories from which reintroductions into suitable habitats could be made later on. Fortunately, N. gracilis is the most widespread and common lowland species and is currently not threatened with immediate extinction.